Explosive composition comprising a nitric acid ester of a polyvalent alcohol and theternary salt mixture of ammonium chloride, an alkali nitrate, and an alkaline earth carbonate



United States Patent 3,357,873 EXPLOSIVE COMPOSITION COMPRISING A NI- TRIC ACID ESTER OF A POLYVALENT ALCO- HOL AND THE TERNARY SALT MIXTURE OF AMMONIUM CHLORIDE, AN ALKALI NITRATE, AND AN ALKALINE EARTH CARBONATE Adolf Berthmann, Leverkusen, Gotthard Kuhn, Ettlingen, and Paul Lingens, Leverkusen, Germany, assignors to Dynamit Nobel Aktiengesellschaft, Troisdorf, Germany, a corporation of Germany N0 Drawing. Filed Aug. 22, 1966, Ser. No. 575,219 Claims priority, application Germany, Aug. 21, 1965, D 48,032 3 Claims. (Cl. 14966) ABSTRACT OF THE DISCLOSURE Explosives having increased resistance to deilagration are disclosed which are characterized by high specific energies which are formed of a mixture of a sensitizing component, i.e., a nitric acid ester of a polyvalent alcohol and a ternary mixture of inorganic salts. The ternary salt mixture is based on ammonium chloride, alkaline earth carbonate and alkali nitrate wherein the molar ratio of ammonium chloride to alkali nitrate amounts to 1.67; ammonium chloride to alkaline earth carbonate amounts to at least 5 and preferably from 5 to 30 and alkali nitrate to alkaline earth carbonate amounts to at least 3 and preferably from 3 to 18.

This invention relates to explosives characterized by increased resistance to deflagration, i.e., safety explosives. More particularly, the invention relates to explosives characterized by an increased resistance to defiagration which are comprised of sensitive explosive components and inorganic salts. The invention also provides a process for manufacturing such safety explosives.

This application is a continuation-in-part of copending application Ser. No. 507,024, filed Nov. 9, 1965, now abandoned.

Explosives are known which contain, in addition to a sensitizing component, ammonium nitrate, ammonium chloride, and calcium carbonate. These explosives are, however, not adequate for the present safety requirements as they are insufficiently resistant to fire damp and other explosive atmospheres. v

When explosives are intended for use in mines, as, for instance, in underground coal mines, they must be characterized by high insensitivity to ignition by fire damp and other explosive atmospheres. The safety explosives as heretofore proposed consist of sensitizing components (a mixture of nitroglycerine and nitroglycol or nitropenta and of the so-called inverse salt pair of alkali nitrate (potassium or sodium nitrate) and ammonium chloride. These explosives behave in a relatively satisfactory manner upon application of thermal stress as compared to the conventional rock blasting explosives and the safety explosives of class 1. However, explosive practice has demonstrated that it is necessary to increase their resistance to deflagration even more, i.e., to increase their safety factor.

It is one of the objects of the invention to produce improved safety explosives.

It is a further object of the invention to produce safety explosives, characterized by increased resistance to deflagration and by an increased insensitivity to explosive atmospheres, particularly fire damp, thereby enabling them to be used in rock blasting, as, for instance, practiced in mining.

3,357,873 Patented Dec. 12, 1967 "ice It is another object of the invention to teach safety explosives for use in rock blasting wherein explosive handling is greatly simplified and blasting effectiveness is vastly increased.

Further objects and advantages will become apparent to those skilled in the art as the description proceeds.

In accordance with the invention it has now been found that explosives highly insensitive to explosive atmospheres and having an increased resistance to deflagration may be obtained by forming mixtures of sensitizing components and inorganic salts, wherein the inorganic salts used are a ternary mixture based on ammonium chloride, alkali nitrates alkaline earth carbonates in a molar ratio of 5:321 (ammonium chloride/alkali nitrate=1.67; ammonium chloride/ alkaline earth carbonate=5; alkali nitrate/alkalineearth carbonate=3). That is, there is utilized in accordance with the aforesaid combination of components sufficient calcium carbonate that the total.

hydrochloric acid produced upon the reaction of the ammonium chloride with alkali nitrate is bound.

Further, in accordance with the invention, it has now been found that the energy of the above explosives can be substantially further increased by allowing only a part of the hydrochloric acid liberated in the reaction of ammonium chloride with alkali nitrate to react with calcium carbonate, i.e., by reducing the calcium carbonate content of the salts. The reduction of the calcium carbonate content within certain defined limits does not substantially decrease the deflagration safety of the explosive. Thus, in order to obtain these particularly high energy explotives, it is proposed that with a molar ratio of ammonium chloride to alkali nitrate of 1.67, there be used an amount of alkali earth carbonates which is sufficient to react with only a part of the hydrochloric acid produced in the re action, in which connection the molar ratio of ammonium chloride to alkali earth carbonate can have a value within the range of greater than 5 to 30 and preferably 10 to 20, and the molar ratio of alkali nitrate to alkali earth carbonate can have a value falling within the range of greater than 3 to 18 and preferably 6 to 12.

In accordance with the invention it has been established that the replacement of the known binary salt mixtures of alkali nitrates and ammonium chloride with the ternary salt mixture of ammonium chloride, alkali nitrates and alkaline earth carbonates results, surprisingly, in an increase in the specific energy of the resulting explosive and simultaneously in explosives inactive to explosive atmospheres and markedly resistant to deflagration.

In the following Equations 1, II, and III, there are set out salt mixtures corresponding to those of the known explosives referred to above. In Equations IV and V, representative salt mixtures of the explosives coming within the scope of the invention, i.e., wherein sufiicient calcium carbonate is present to react with all of the HCl are set out.

Table I shows the thermodynamic data for the reaction Equations I-V.

TABLE I Salt Mixt. Oz Expl. Expl. Expl. Spec. Solid of the balance, heat, temp., gas encrgy,* explosion Reactions percent K cal./ K. vol. nut/kg. products,

kg. l./kg. percent in mols per kg. and the explosion temperature in K.

The known salt mixture corresponding to Equation I ual salts. The amount of sensitizing explosive components has a high specific energy, out also a high explosion ternperature and a small proportion of solid explosion products. Explosives with these characteristics do not, however, meet the present high requirements for safety explosives. In addition, the exact grinding as well as the processing of the ammonium nitrate required for use in such explosives can be accomplished only with great difliculty because of its high tendency to absorb moisture as well as its low transition point (32 C.). The molar ratio of ammonium chloride/ammonium nitrate/alkaline earth :arbonate in these explosives is 2:3: 1.

The reaction of the inverse salt pairs (Equations II and III) is characterized by a very high oxygen balance, in contrast to the salt combinations according to the invention, where the observed oxygen balance is zero. The molar ratio of the alkali nitrate to ammonium chloride in Equations II and III is 1:1.

Further, it is readily apparent from the above table that the specific energy and the solid explosion components are higher in the equations reciting the ternary salt mixtures than in the equations reciting the inverse sa-lt pair. (In this connection compare Equation II with IV and Equation III with V.) Although the calcium carbonate which is added to the inverse salt pair is generally considered as an inert constituent in explosive mixtures, the explosives thereby obtained have a higher specific energy, since the CaCO in these instances takes part in the reaction.

In the following Equations VI, VII, VIII and IX, representative salt mixtures of the explosives coming within the scope of the invention wherein there is present insufficient CaCO to react with all of the HCl produced ar set out:

(VI) 2ONH Cl+ IZKNO +CaCO l2KCl CaCl 6HC1+ 371-1 0 |-16N CO The sensitizing components for use in the instant inven- :ion are the known nitric acid esters of polyvalcnt alcohols, such as glycol dinitrate, glycerin trinitrate (nitroglycerin), pentaerythritol tetranitrate (nitropenta) and the like. Mixtures. of these nitric acid esters can also be used to great advantage.

Alkali nitrates are used in the preparation of the new explosives. Preferably, the nitrates of potassium and so- ;lium are utilized.

As alkaline earth oar bonate, calcium carbonate is pref- :rably used, but it is also possible to use magnesium cardonate, barium carbonate or mixed carbonates, as for ,nstance dolomite.

The reaction of the ternary salt mixture during detona- :ion also depends, as has been described above for the ;alt pair alkali nitrate/ ammonium chloride, on the fineiess of grain of the salts, i.e., particle size of the individtained when a fineness of grain is chosen for the ternary salt mixture in which at least 30% and at most pass a sieve of 0.1 mm. mesh width. The amount of the sensitizing component in this case must be between 6 and 15 wt. percent, preferably between 8 and 12 wt. percent.

It is also possible, in accordance with the invention to produce explosives having an oxygen excess. This is accomplished by the addition of alkali nitrate and/or of an equimolar salt mixture based on alkali nitrate and ammonium chloride. The molar ratio of ammonium chloride/ alkali nitrate should, in this case, however, not drop below a value of 1.285, while the molar ratio of mayincrease up to a value of 9, and the molar ratio of NaNO /CaCO' may increase up to a value of 7. The calculation of the oxygen balance should be effected under the assumption that the hydrochloric acid liberated is not oxidized under the blasting conditions. Equations X and XI illustrate the invention where an inverse salt pair is added to the ternary salt mixture. 5NH Cl+3MeNO +CaCO --3MeCl+CaCl The salt mixture as set out in Equation X where MeNO' designates potassium nitrate has, for example, an oxygen balance of +32%. The molar ratios of The corresponding values for the salt mixture of Equation XI are:

Oxygen balance: +4.9 NH Cl/MeNO ='1.285 NH Cl/CaCO =9 MeNO /CaCO 7 Specific energy=23.l kcal./ kg.

in a molar ratio of 1:1. The alkali nitrate or the salt mixture of alkali nitrate and ammonium chloride added is, here, however, not taken into consideration in the calculation of the molar ratio of ammonium chloride/ alkali nitrate/alkaline earth carbonate in the explosive.

Furthermore, known inert materials as, for example, common salt, alumina, silicates, iron oxide, etc., may also be added to the explosives according to the invention in order to increase additionally their safety toward explosive atmospheres or their shelf life.

The advantages of the explosives according to the invention are that their resistance to deflagration is improved along with a simultaneous increase of energy.

The invention will be further illustrated by a detailed description in connection with the following specific examples of the practice of it:

EXAMPLES 1ac Three explosives having a composition of salts conforming with that set out in Equations III, V, and VI were prepared in the conventional manner by mixing.

The three explosives proved entirely safe toward a methaneair mixture when tested according to the German process for determination of explosive-atmosphere safe explosives of class III (see Ahrens article, Nobel Hefte, May 1959).

Comparative Example 1a. Explosive according to Equation III (NH Cl/KNO =1) consisting of:

Weight percent tion In rens, Nobel Hefte, May 1959, p. 126), 6 more or less distinct reactions of the explosive occurred in 10 experiments.

When a cartridge of the explosive was heated in an oven at 140 C., the same having been provided with a kieselguhr sheath so that heat will be accumulated, a temperature increase of about 600 C. was observed in the explosive.

1bExplosive according to the invention Explosive according to Equation V (NH Cl/KNO 1.67; NH Cl/CaCO =5; KNO /CaCO =3) consisting of:

Weight percent Nitroglycerin 5.22 Nitroglycol 3.48 Potassium nitrate 78% 01 m 41.28 Ammonium chloride 65% 0.1 mm 36.40

Calcium carbonate 85% 0.1 mm 13.62

Weight percent Explosive properties:

Excess oxygen +02%. Specific energy 33.5 mt./kg.

5 Det. transmission exposed on sand (car tridge diameter 32 mm.)

Resistance to deflagration No reaction of the explosive occurred during 10 experiments in the Audibert tube.

When a cartridge of the explosive, which had been surrounded by a sheath of kieselguhr, was heated in the oven to 200 C., a temperature increase of about 20 C. was measured in the explosive.

]c-Explosive according to the invention Explosive according to Equation VI (NH Cl/KNO =1.4; NH Cl/CaCO =7; KNO /CaCO =5) consisting of:

Weight percent Nitroglycerin 5.22

Nitroglycol 3.48

Potassium nitrate 75% 0.1 .mm. 47.09

Ammonium chloride 62% 0.1 mm 34.89

Calcium carbonate 85% 0.1 mm 9.32

Explosive properties:

Excess oxygen +32%.

Specific energy 32.7 mt./kg.

Det. transmission exposed on sand (cartridge diameter 32 mm.)

Resistance to deflagration No reaction of the explosive occurred during 10 experiments in the Audibert 40 tube.

When a cartridge of the explosive, which had been surrounded by a sheath of kieselguhr, was heated to 200 C. in the oven, a temperature increase of 30 C. occurred.

A comparison of the above explosives demonstrates that the composition according to the invention has a relatively high specific energy as well as a most favorable behavior towards thermal stress.

EXAMPLE 2 Two explosives were prepared whose salt composition conformed to Equations III and V.

Explosive according to Equation III (NH Cl/NaNO =1) consisting of:

Weight percent Nitroglycerin 6.6 Nitroglycol 4.4 Sodium nitrate 70% 0.1 mm 54.63 Ammonium chloride 65% 0.1 mm 34.37

Explosive properties:

Excess oxygen +10.5%. Specific energy 35.7 mt./kg. Det. transmission exposed on sand (cartridge diameter 32 mm.) 35 cm.

Safety toward methane/ air mixture This explosive was, when tested according to the German specifications for class II safety explosives (Ahrens, Nobel Hefte, May 1959) safe toward a methane/air mixture, with 6 cartridges around the rim.

Resistance to deflagration 7 more or less distinct reactions of the explosive occurred during 10 experiments carried out in the Audihert tube.

When the explosive, which had been surrounded by a ieselguhr sheath, was heated to 120 C. in the oven, at :mperature increase of 650 C. occurred.

.xplosive according to Equation V (NH C1/NaNO 7; NH Cl/CaCO =5; NaNO /CaCO =3 consisting Weight percent Nitroglycerin 6.6 Nitroglycol 4.4 Sodium nitrate 77% 0.1 mm 36.45 Ammonium chloride 62% 0.1 mm 38.23 Calcium carbonate 85% 0.1 mm 14.32

Explosive characteristics:

Excess oxygen +02%. Specific energy 37.6 mt./kg.

Det. transmission exposed on sand (cartridge diameter 32 mm.) 40 cm. Resistance to methane/ air mixture The explosive was, when EXAMPLE 3 An explosive was prepared which contained:

11 wt. percent of sensitizing components 2.0 wt. percent of combustible substances 5.86 wt. percent of sodium nitrate 80.94 wt. percent of a salt mixture according to Equation VI, and

0.2 wt. percent of alumina as an inert material.

The additional saltpeter of 5.86% was exactly sufficient for complete oxidation of the wood flour.

Composition: Weight percent Nitro glycerin 6.6 Nitro glycol 4.4 Wood flour 2.0 Alumina 0.2

Sodium nitrate (75 wt. percent) 0.1 mm 44.10 Ammonium chloride (65 wt. percent) 0.1

mm. 33.68 Calcium carbonate (80 wt. percent) 0.1

Weight percent Explosive characteristics:

Excess oxygen +2.9% Specific energy 40.3 mt./kg.

Det. transmission exposed on sand, cartridge diameter 35 cm. Resistance to methane/air mixture The explosive was, when tested according to the German specifications for class II explosives (Ahrens, Nobel Hefte, May 1959) resistant to a methane/ air mixture, with 8 cartridges around the rim. Resistance to deflagration No reaction of the explosive occurred during 10 experiments in the Audibert tube.

If a cartridge of the explosive, surrounded by a kieselguhr sheath, was heated to 200 C. in the oven, a temperature increase of 50 C. occurred.

EXAMPLE 4 Four safety mining explosives were prepared in the conventional manner by mixing together.

5.1% nitroglycerin 3.4% nitroglycol, and

91.5% of a salt mixture of potassium nitrate, ammonium chloride and calcium carbonate. The composition of the explosives is indicated in Table II.

TABLE II Percent by weight Components Nitroglyoerin 5. l 5. 1 5. 1 5. 1 Nitroglycol 3. 4 3. 4 3. 4 3. 4 Ammonium chloride 41. 1 40. 6 39. 4 36. 5 Potassium nitrate 46. 6 45. 9 44. 7 41. 4 Calcium carbonate 3. 8 5.0 7. 4 13. 6

The particle size of the salts was as follows: NH C1: 65% less than 0.1 mm., KNO 72% less than 0.1 mm., CaCO less than 0.1 mm.

All four explosives were safe with respect to a methane/air mixture when tested in accordance with the German specification for Safety Mining Explosives of Class III (see Mining Ordinance on the Use of Explosives in Mining of January 28, 1959; cf. also article by Ahrens, Nobel Hefte of May 1959 and had a detonation transmission of 50 cm. (lying free on sand).

In all four salt mixtures, the molar ratio of ammonium chloride to alkali nitrate was 1.67. This is the same molar ratio of ammonium chloride to alkali nitrate as set out in the above examples to the salt mixtures VI, VII, and VIII of the invention. The molar ratios of NH Cl to CaCO and of KNO to CaCO however were changed. In the case of salt mixtures VI, VII, and VIII, they had molar ratios of 20, 15, and 10 for NH Cl:CaCO respectively, (above examples NH Cl:CaCO =5), the molar ratios of 6, 9, and 12 for KNO :CaCO (above examples KNO :CaCO =3). The salt mixture IX corresponded in its composition to the mixtures described above having the molar ratio NH Cl:KNO :CaCO =5 13:1.

If one considers that the hydrochloric acid liberated in Equations VI-VIII as being no longer combustible under actual practical reaction conditions, then all four salt mixtures have an oxygen balance of 0. For the specific energies (product of the gas constant R by the volume of smoke in mols/kg. multiplied by the explosion temperature in K.), of the salt mixtures, the following values were calculated:

Salt mixtures: Mt./kg. 1 29.3 2 28.7 3 27.6 4 24.6

The salt mixture X which corresponded to the mixtures described in Examples 1-3 had the lowest specific energy. The explosives of the invention, having the salt mixtures l, 2, and 3, set out in the instant examples, are accordingly of higher energy than the mixtures set out in Examples l-3.

The behavior of these three mixtures with respect to heat was determined by the following tests:

A cartridge of each of the four explosive mixtures examined was surrounded by a kieselguhr jacket and heated to the test temperature of 130 C. in a furnace. While under these test conditions the ordinary safety mining explosives of Classes II and III reacted substantially and heated up to about 650 C. to 800 C. In the explosive mixtures 1, 2, and 3 there was no reaction of the salts and an increase in temperature of only about 25 C. was observed.

If the customary safety mining explosives of Class II and III upon blasting in actual practice should have to remain for some time under the influence of the hot smoke of a neighboring blast, there is a certain probability of igniting the fire damp since a methane/air mixture ignites at a temperature of 650 C. and with an induction time of only 10 seconds.

A 5% coal dust was mixed with the four explosives of the example and the deflagration behavior of these explosive mixtures which contain coal dust was examined in an Audibert tube (cf. article by Ahrens in Nobel Hefte of May 1959, page 126). The following defiagration probabilities were obtained in tests:

Percent Mixture l 20 Mixture 2 7 Mixtures 3+4 0 Under the same conditions pronounced reactions occurred with a deflagration probability of in the case of the ordinary safety mining explosives.

It can be seen from the examples that the advantage of the new explosives over the known safety mining explosives of Classes II and III resides in their considerably improved defiagration safety, while the advantages of the compositions 1-3 of Example 4 and other compositions of this type over the mixtures of Examples 1-3 reside in the increase in their energy.

We claim:

-1. A safety explosive characterized by an increased resistance to defiagration having a high specific energy comprising a mixture of 6 to 15 weight percent referred to the explosive of a sensitizing component selected from the group consisting of nitric acid esters of polyvalent alcohols and a ternary mixture of inorganic salts, the latter comprising ammonia chloride, alkali nitrate and alkaline earth carbonate wherein the molar ratio of ammonium chloride to alkali nitrate amounts to 1.67, ammonium chloride to alkaline earth carbonate amounts to at least 5, and alkali nitrate to alkaline earth carbonate amounts to at least 3.

2. A safety explosive according to claim 1, wherein the molar ratio of ammonium chloride to alkaline earth carbonate amounts to 5 and the molar ratio of alkali nitrate to alkaline earth carbonate amounts to 3.

3. A safety explosive according to claim 1, wherein the molar ratio of ammonium chloride to alkaline earth carbonate amounts to from 5 to 30 and the molar ratio of alkali nitrate to alkaline earth carbonate amounts to from 3 to 18.

References Cited UNITED STATES PATENTS 2,680,067 6/ 1954 Davidson 149-62 X 2,829,036 4/1958 Berthmann et al 149-62 2,904,420 9/1959 Holker 149-61 X CARL D. QUARFORTH, Primary Examiner.

BENJAMIN R. PADGETT, Exam'ner.

S. I. LECHERT, JR., Assistant Examiner. 

1. A SAFETY EXPLOSIVE CHARACTERIZED BY AN INCREASED RESISTANCE TO DEFLAGRATION HAVING A HIGH SPECIFIC ENERGY COMPRISING A MIXTURE OF 6 TO 15 WEIGHT PERCENT REFERRED TO THE EXPLOSIVE OF A SENSITIZING COMPONENT SELECTED FROM THE GROUP CONSISTING OF NITRIC ACID ESTERS OF POLYVALENT ALCOHOLS AND A TERNARY MIXTURE OF INORGANIC SALTS, THE LATTER COMPRISING AMMONIA CHLORIDE, ALKALI NITRATE AND ALKALINE EARTH CARBONATE WHEREIN THE MOLAR RATIO OF AMMONIUM CHLORIDE TO ALKALI NITRATE AMOUNTS TO 1.67, AMMONIUM CHLORIDE TO ALKALINE EARTH CARBONATE AMOUNTS TO AT LEAST 5, AND ALKALI NITRATE TO ALKALINE EARTH CARBONATE AMOUNTS TO AT LEAST
 3. 